This invention relates to a resist material used for forming a resist pattern by application of radiation such as electron beams, X-rays and ultraviolet rays.
In order to meet the rising request for higher integration capacity of the semiconductor integrated circuits in recent years, there has been proposed the etching method which is capable of forming a fine and minute pattern on the substrate by utilizing radiation of short wave length such as electron beams, X-rays and ultraviolet rays.
This invention is to provide a resist material used in such etching method utilizing radiations of said type, and more particularly the invention is intended to provide the above-said kind of positive resist material which can be solubilized in the developing solvent upon exposure to radiation.
Poly(methyl methacrylate) (hereinafter referred to as PMMA), crosslinked PMMA and polystyrene sulfone are known as typical examples of the positive type resist materials, but these materials are unsatisfactory in respect of sensitivity. For instance, the minimum incident charge of electron beams required for the irradiation is as high as 5.times.10.sup.-5 Coulomb/cm.sup.2 (hereinafter abbreviated as C/cm.sup.2) in the case of PMMA, 0.8.times.10.sup.-5 C/cm.sup.2 in the case of crosslinked PMMA, and 1.times.10.sup.-5 C/cm.sup.2 in the case of polystyrene sulfone, and for drawing for example a 3-inch square mask pattern, it needed to apply fairly intense electron beams for a prolonged period of time which could amount to the order of days.
An object of this invention is to provide a resist material having sensitivity to radiation of the charge level which is one to two figures lower than that required in use of the conventional materials.
Another object of this invention is to provide a high-molecular weight resist material which can well stand use with the chromium etching solutions.
The resist material provided according to this invention comprises as principal constituent poly(ethyl .alpha.-cyanoacrylate), poly(ethyl .alpha.-amidoacrylate) or a binary copolymer thereof or a ternary copolymer composed of said two substances plus polymethacrylonitrile, and has sensitivity to the electron beams of the minimum incident charge of 5.times.10.sup.-7 C/cm.sup.2 or the X-rays or ultraviolet rays of the incident charge of the order of 20 mJ/cm.sup.2. This resist material can also stand use with the chromium etching solutions.